The present invention relates to ceramic cups having a body and a handle and to injection molded articles having sprues, and more particularly to an injection molded ceramic cup having an integral handle and an injection molded article having a concealed sprue.
Cups made of ceramic materials (such as bone china or earthenware) have been made without handles by a variety of different procedures, including injection molding. Where the cup includes both a body and a handle (like a tea cup or mug), the body and handle cooperatively define an aperture for passage therethrough of at least a portion of a user's finger. The term "cup" as used hereinafter will refer to a cup having a body and a handle.
Generally the prior art teaches the manufacture of ceramic cups by the separate manufacture of the body and the handle, and then the joining of the handle to the body in a cementing operation. As a result, the body/handle joint has always been a point of weakness in prior art cups, and the failure of the joint has resulted in many cups being discarded, both during the manufacturing process and during use by the consumer. Prior art manufacturing techniques also placed severe limitations on the design shapes which could be economically produced.
In order to avoid the difficulties associated with the after-formed body/handle joint, the art has relied upon a variety of different manufacturing techniques. U.S. Pat. No. 4,533,311 and U.S. Pat. No. 4,713,204 disclose the manufacture of a ceramic cup having an integral handle by an isostatic compression technique wherein the mold halves are somewhat spaced apart when the ceramic material is introduced into the mold and thereafter closed in order to produce the isostatic pressure. (By way of contrast, in an injection molding process, the mold halves are closed when the ceramic material is introduced into the mold, and the pressure is applied by the ceramic material itself being introduced into the closed mold or die cavity under pressure). U.S. Pat. No. 1,677,611 closes means for shaping a cup with an integral handle using a complex mold which requires a detachable portion in which the handle is formed. U.S. Pat. No. 1,885,303 discloses the formation of a cup in a mold which requires the use of pivotable levers in order to form the desired finger opening. U.S. Pat. No. 3,357,056 discloses the formation of a double-walled plastic cup with an integral handle through a compression molding.
These alternative manufacturing techniques are substantially more expensive and/or more burdensome than injection molding, especially where the mold must include detachable portions or movable elements within the die cavity. Additionally, these alternative processes fail to provide the distinctive distinguishing features of an injection molded process--for example, the ability to form thick and thin walls adjacent to one another, the ability to have sections of the cup (such as the design of the foot of the cup) pierced, and the ability to make unusual designs on the inside as well as the outside of the cup. For example, isostatic pressing present serious problems of die design and mold filling where thick and thin sections are to be formed adjacent to one another. By way of contrast, injection molding results in the ceramic material being uniformly distributed throughout the die cavity in the form of a flowable mass.
Any injection molded article, whether ceramic or not, will invariably have an unsightly irregularity or sprue at the point where the material to be molded has been injected into the mold, this point typically being referred to as "the entry point." The sprue at the entry point may be either "positive" (meaning that it extends outwardly from the adjacent surface) or "negative" (meaning that it represents a depression or cavity in the adjacent surface). A negative sprue may be formed either during the molding process or later when the manufacturer attempts to break off or otherwise remove a positive sprue. Regardless of whether the sprue is positive or negative, it typically detracts from the appearance of the finished article. Accordingly, the sprue is frequently formed in a relatively concealed portion of the article, such as the base or foot of a cup or plate. This does not completely solve the problem however, since a prospective purchaser will typically invert a cup or plate in order to note any indicia thereon which may indicate the manufacturer, the quality, or the like. Indeed, it is frequently precisely at the location of the sprue that the customer seeks the aforementioned indicia (e.g., a trademark, logo or quality indicator) and, instead or in addition, finds the unsightly sprue.
Accordingly, it is an object of the present invention to provide an injection molded ceramic cup wherein the body and handle are of integral, one-piece, unitary construction formed in a single injection molding operation.
Another object is to provide such a cup which affords one or more of the advantages of an injection molding manufacturing process.
A further object is to provide an injection molding process for the manufacture of such a cup.
It is also an object of the present invention to provide such an injection molded ceramic cup having a concealed sprue.
It is another object to provide an injection molded article (whether it be ceramic or not) having a concealed sprue.
It is a further object to provide such an article which appears to be custom made.
Yet another object of the present invention is to provide a process for manufacturing such an article.